Field of Invention
The present invention relates to a method of controlling four-wheel driving of a vehicle, and more particularly, to a method of controlling four-wheel driving of a vehicle which improves an uphill-driving response speed and uphill-driving ability, when a vehicle starts, particularly, on an uphill, by controlling first the driving force of the rear wheels of a four-wheel drive vehicle in accordance with a degree of slope of a ground on which the vehicle is.
Description of Related Art
In general, in four-wheel drive vehicles, which simultaneously drive the front wheels and the rear wheels, using a transfer case that distributes driving torque from an engine to the front wheels and the rear wheels, the driving force is distributed to the tires of the front and rear wheels, when the vehicles are driven on a slippery road such as a snowy road or an icy road or need large driving force, for example, on a sandy ground, a steep slope, and a muddy road, so the driving tires less slip on the roads, and thus stability in traveling and the ability of running on the grounds are improved.
The four-wheel drive vehicles require a control unit that appropriately distributes the driving force from the engine to the front wheels and the rear wheels, depending on the surrounding environment, and increases/decreases the driving torque by determining which driving wheels are given too much driving force on the basis of the difference in number of revolutions of the front and rear wheels.
FIG. 1 is a diagram illustrating the configuration of a common four-wheel drive vehicle in a normal state, in which a transfer of the four-wheel drive vehicle, in a normal state, appropriately distributes the driving force from an engine 1 to the front wheels and the rear wheels, depending on the surrounding environment of the vehicle that is traveling.
The transfer 40 is connected to a controller 30 and distributes the driving force to the front and rear wheels and the controller 30 determines whether the vehicle slips on the basis of the rotation speeds of the wheels 20a, 20b, 20c, and 20d and controls the transfer 40 distributing the driving force to the front and rear wheels.
However, in the four-wheel drive vehicles, when the vehicles start after stopping on a slope, more loads are applied to the rear wheels than the front wheels, so the friction force between the front wheels and the ground relatively decreases, whereas the friction force between the rear wheels and the ground increases.
Therefore, there is a problem in that when front wheels are rotated by relatively large driving torque, the driving force of the front wheels is larger than the friction force, so the front wheels further slip while the driving force of the rear wheels relatively decreases and the force that pushes the vehicle by the rear wheels relatively decreases, so the ability of starting and uphill-driving of the vehicle decreases.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.